Each year in the United States at least 2 million people become infected with antibiotic-resistant bacteria and at least 23,000 people die as a direct result. Overuse of antibiotics is a key factor driving the emergence of antibiotic-resistant bacteria. This has led federal agencies to recommend acute care facilities have antimicrobial stewardship programs and record antimicrobial utilization data using the National Quality Forum (NQF)-endorsed Centers for Disease Control and Prevention (CDC) National Healthcare Safety Network (NHSN) Antimicrobial Use Measure. Many believe that it is inevitable that antimicrobial utilization data will be used to judge performance of hospitals and as a pay-for-performance outcome. The gap in knowledge is that current risk adjustment methods used by the CDC for antimicrobial utilization data are sub-optimal because methods to adjust for patient comorbid conditions do not exist. Our long-term goal is to improve the quality and validity of publicly reported metrics for healthcare quality including healthcare-associated infection and antimicrobial utilization data. The overall objective of this proposal is to determine which comorbid conditions should be used for risk adjustment of antimicrobial utilization data. Our central hypothesis is that comorbid conditions identified by ICD codes that are easily obtained electronically from hospitals across the United States can be used to improve risk adjustment of antimicrobial utilization metrics. The rationale for this proposal is the need for further advancement in risk adjustment methodology for antimicrobial utilization metrics. Now is the ideal time to establish appropriate risk adjustment measures for antimicrobial use because CMS has not yet incorporated antibiotic use into its value-based purchasing system. Comorbid conditions are a logical starting point as they have been proven to be significant predictors of other infectious disease outcomes and are easy to obtain. We plan to test our central hypothesis and, thereby, accomplish the objective of this proposal by pursuing the following specific aims: Aim 1: Perform a cohort study of adult patients admitted to multiple hospitals across the United States to determine which electronically obtained comorbidities are risk factors for different antibiotic utilization metrics. Aim 2: Demonstrate that risk adjustment using comorbid conditions affect hospital rankings of antimicrobial utilization. The expected outcome of this research is the identification of comorbid conditions using ICD codes for that can be used to risk adjust antimicrobial utilization data. The implementation of these by the CDC and CMS will lead to more valid publically available data. The significance of our research is that it will identify easily available electronically comorbid conditions that could be used to better risk adjust these antibiotic utilization metrics. The proposed research is innovative in that no one has explored the use of ICD codes for risk adjustment of antimicrobial utilization data. This work challenges the existing paradigm of risk adjustment of antimicrobial utilization metrics. In addition, this project has the potential to significantly impact antimicrobial utilization metrics and pay-for-performance methods.